Conventionally, as means for a user to recognize a reception state of a terminal before starting data communications, there has been a method for displaying the reception state on a screen of the terminal using antenna marks. In this method, the state is represented by varying the number of antennas corresponding to the reception level on a pilot channel, for example (e.g. Patent Document 1). When the number of antenna marks is a few which is displayed on the screen of the terminal, the user is capable of having an assumption that the reception state is poor, and it is thus difficult to receive data of a high transmission rate. Meanwhile, when the number of antenna marks is large which is displayed on the screen of the terminal, the user is capable of having an assumption that the reception state is good, and it is thus possible to receive data of a high transmission rate. In this way, according to the number of antenna marks, the user is capable of indirectly recognizing the transmission rate and quality of service allowed by the transmission rate.
Meanwhile, there is known an HSDPA (High Speed Downlink Packet Access) system, as a mobile communication system using a communication scheme of switching between transmission rates corresponding to reception quality of a terminal after starting data communications. In HSDPA, a terminal measures the reception quality, and notifies a base station of a transmission rate enabling reception in the terminal based on the measured reception quality. The terminal in HSDPA measures as reception quality a signal to noise ratio in pilot channel signal that is a signal always transmitted from the base station, selects receivable transmission rate candidates using information of the measured reception quality, and transmits information of the selected transmission rate to the base station. The base station receives the information of the transmission rate from a plurality of terminals, selects a modulation scheme suitable for packet data to transmit to a terminal in good reception state to modulate the data, while performing processing called scheduling, and then, transmits the packet data to the terminal.
As a service to provide to a user using the transmission rate measured after starting data communications, such a service is known that indicates download prediction time in best-effort type service such as the Internet. The download prediction time is obtained by periodically monitoring the transmission rate of a short interval after actually starting the download, and dividing a remaining data amount by throughput.
Patent Document 1
Japanese Laid-Open Patent Publication 2002-44036